A method for analyzing the flexible assembly deviation of laminated structural parts considering interference connection

Abstract

The present invention discloses a method for analyzing the flexible assembly deviation of a laminated structure under interference connection, which is specifically implemented as follows: obtaining the initial stiffness matrix of the wall panel parts; using flexible tooling to position and clamp the wall panel parts according to the N-2-1 positioning principle; positioning parts are positioned and clamped according to the positions of the wall panel parts, and the positioning parts are interference connected with the wall panel parts one by one. After each interference connection of a positioning part, the springback amount of all key feature points on the wall panel parts after the interference connection of the positioning part is calculated based on the influence coefficient method, and the springback deformation amount of the wall panel parts at the mating surface of the next positioning part and the wall panel parts is calculated, until all positioning parts are clamped, and the displacement of the last wall panel part concerned point is recorded, that is, the flexible assembly deviation of the laminated structure is obtained. The present invention improves the accuracy of assembly deviation analysis based on the consideration of interference internal stress.

Description

Technical Field

[0001] The invention belongs to the technical field of flexible component assembly, and relates to a method for analyzing flexible assembly deviation of a laminated structural component considering interference connection. Background Art

[0002] Laminated thin-walled structural parts made of fiber-reinforced materials have the characteristics of high performance and light weight, and are widely used in aircraft skin parts. Interference fit is its main connection method. It introduces interference stress on the material surface during the connection process, which can improve the fatigue life of the connection. However, thin-walled composite parts have the characteristics of large size, low stiffness, anisotropy, etc., and are accompanied by shape errors, positioning errors, and installation errors of the parts themselves during the assembly process, which inevitably cause deformation, thereby affecting the assembly quality of subsequent aircraft components and final assembly.

[0003] Composite panel parts, such as wing box skins and nose fairings, are often positioned and clamped using flexible tooling based on the N-2-1 positioning principle. However, due to the manufacturing errors of the panel parts themselves, the manufacturing errors of the assembly jigs, and the introduction of installation positioning errors, gaps or interferences are generated in the assembly of flexible parts. Although fixtures are used to force assembly to eliminate the relevant gaps or interferences, the flexible parts will deform to a certain extent after the assembly force is released. In 1997, Liu and Hu decomposed the assembly of flexible parts into four steps: positioning, clamping, assembly, and release and rebound. Based on the use of finite element analysis and statistical methods, the influence coefficient method (MIC) was proposed. The linear relationship between part deviation and assembly rebound deviation was established by constructing a sensitive matrix. Composite panel parts are connected and assembled as a whole through interference connection such as riveting and high-locking bolts. The hole wall at the connection inevitably introduces stress along the layer. Since the panel parts are thin-walled flexible parts, they will produce obvious rigidification effects, resulting in a complex assembly rebound deformation process. The traditional influence coefficient method will produce a relatively large deviation in the analysis results. Lin Jia et al. found two different assembly conditions that produce a large stress stiffening effect in thin-walled structures, and gave a practical finite element simulation analysis case. It was found that the vertical bending stiffness of a homogeneous metal plate with a size of 200×200×1mm would increase by 82.3% under a stretch of 0.01% of the total length, indicating that the stiffening effect of thin-walled parts during the assembly process cannot be ignored. Summary of the invention

[0004] The purpose of the present invention is to provide a method for analyzing flexible assembly deviation of laminated structural parts under interference connection, which improves the accuracy of assembly deviation analysis based on the consideration of interference internal stress.

[0005] The technical solution adopted by the present invention is a method for analyzing the flexible assembly deviation of a laminated structural part under interference connection. The laminated structural part includes a wall panel part and a positioning part. The positioning part is clamped and positioned by a fixture. The wall panel part and the positioning part are assembled by a flexible tooling. The wall panel part and the positioning part are interference connected. The method is specifically implemented according to the following contents:

[0006] Get the initial stiffness matrix of the panel parts;

[0007] Flexible tooling is used to position and clamp the wall panel parts according to the N-2-1 positioning principle;

[0008] According to the position of the wall panel parts, the positioning parts are positioned and clamped, and the positioning parts are interference connected with the wall panel parts one by one. After each interference connection of a positioning part, the rebound amount of all key feature points on the wall panel parts after the interference connection of the positioning parts is calculated based on the influence coefficient method, and the rebound deformation of the wall panel parts at the mating surface of the next positioning part and the wall panel parts is calculated, until all the positioning parts are clamped, and the displacement deviation of the key feature points of the final wall panel parts is recorded and obtained.

[0009] The present invention is also characterized in that:

[0010] The initial stiffness matrix of the siding part is obtained by performing finite element analysis on an ideal model of the siding part, and obtaining the initial stiffness matrix of the siding part by setting material property parameters of the siding part.

[0011] The positioning parts are interfered with the wall panel parts one by one. After each positioning part is interfered, the springback amount of all key feature points on the wall panel parts after the positioning part is interfered with is calculated based on the influence coefficient method, and the springback deformation amount of the wall panel parts at the mating surface of the next positioning part and the wall panel parts is calculated until all positioning parts are clamped. Specifically:

[0012] Measure the gap value at the characteristic point of the mating surface between the positioning part and the wall panel part; clamp the positioning part by a fixture and measure the clamping force of the fixture; make an interference connection between the wall panel part and the positioning part, and calculate the stress field along the layer at the interference connection of the wall panel part; load the clamping force of the fixture and the stress field along the layer at the interference connection of the wall panel part onto the finite element model of the wall panel part, and obtain the global stiffness matrix of the wall panel part after the interference connection; unload the fixture on the positioning part, the wall panel part is deformed, and the rebound amount of all key characteristic points on the wall panel part after the interference connection of the positioning part is obtained based on the influence coefficient method, and according to the rebound amount of all key characteristic points on the wall panel part obtained at this time, calculate the rebound deformation amount of the wall panel part at the mating surface of the positioning part and the wall panel part in the next clamping;

[0013] Repeat the above operation each time a positioning part is clamped and fixed. In this way, until the last interference connection hole is connected, the springback amount of all key feature points is calculated.

[0014] The specific gap value measured at the characteristic point of the matching surface between the positioning part and the wall panel part is:

[0015] Measure the manufacturing error V of the key feature points of the wall panel parts and the positioning parts in the normal direction respectively s j and V t j , the positioning part is the jth positioning part, V s j is the manufacturing error of the panel parts in the normal direction, V t j is the manufacturing error of the positioning part in the normal direction, 1≤j≤n, n is the total number of positioning parts, n is a natural number not equal to 0, and the clearance value between the jth positioning part and the wall panel part at the corresponding key feature point

[0016] The positioning part is clamped by a fixture, and the clamping force of the fixture is measured as follows:

[0017] The jth positioning part is clamped by a fixture so that the jth positioning part and the matching surface of the wall panel part are completely fitted together. The force sensor of the fixture installed on the jth positioning part is used to measure, collect and record the three-axis forces of the measured point, which are F n 、F τ 、F ξ .

[0018] The wall panel parts are connected with the positioning parts through interference, and the stress field along the layers at the interference connection of the wall panel parts is calculated as follows:

[0019] Connect the jth positioning part to the wall panel part through interference connection, solve the internal stress of the wall panel part at the interference connection through finite element analysis, and obtain the stress field distribution σ around the interference connection j .

[0020] The springback amount of all key feature points on the wall panel parts after the interference connection of the positioning parts is calculated based on the influence coefficient method. According to the springback amount of all key feature points on the wall panel parts obtained at this time, the springback deformation amount of the positioning parts and the matching surfaces of the wall panel parts in the next clamping is calculated as follows:

[0021] Based on the linear elastic assumption, the gap value between the jth positioning part and the panel part at the corresponding key feature point is As the input deviation, a linear relationship between the deviation source deviation and the assembly deviation is established, and the influence coefficient method is used to establish a linear relationship between the gap between the wall panel parts and the positioning parts at the interference connection point and the springback of the interference connection:

[0022]

[0023] In formula (20), is the springback amount of all key feature points on the panel parts after the jth positioning parts are interferingly connected, [S] is the sensitivity matrix;

[0024] The initial stiffness matrix of the panel part [K n ], calculate the unit displacement U generated at the clamping point of the wall panel parts under the loading stiffness i , the clamping force F required at the clamping point i , F i It is also equal to the unit rebound force of each clamping point when the jth positioning part fixture is released;

[0025] [F i ]=[K n ]·U i (twenty one)

[0026] In formula (21), F i represents the unit rebound force of each clamping point when the j-th positioning part fixture is released, [F i ] indicates that the clamping point produces a unit displacement U i Unit clamping force matrix under ;

[0027] The unit rebound force F i Load it onto the assembly to calculate the deformation of the panel parts, where the stiffness matrix of the assembly is the global stiffness matrix of the panel parts after interference connection [K j ],

[0028]

[0029] According to formula (22), the unit rebound deformation U of the wall panel parts under the unit rebound force is calculated j ;

[0030] Calculate the springback deformation of the panel parts: Set the gap value Substitute into formula (20) to obtain the unit springback deformation of the wall panel part The influence coefficient matrix [S] is:

[0031] [S]=[K n ] -1 ·[K j ]·U j (twenty three);

[0032] The springback deformation of the wall panel part at the mating surface of the next positioning part and the wall panel part is:

[0033]

[0034] In formula (24), It represents the springback deformation of the wall panel part at the mating surface between the j+1th positioning part and the wall panel part after the jth positioning part is interfered with. It represents the springback deformation of the wall panel part at the mating surface between the j+1th positioning part and the wall panel part before connecting the jth positioning part.

[0035] Final displacement of key skin feature measurement points

[0036] The beneficial effects of the present invention are:

[0037] The present invention provides a method for analyzing the flexible assembly deviation of laminated structural parts under interference connection. It focuses on the flexible assembly of composite material wall panel parts and takes into account the actual assembly process and the changes in the force of the parts at the positioning points. It can accurately derive the assembly deviation of the composite material wall panel parts caused by the interference connection, help analyze the influence of the interference connection on the assembly deviation of the composite material wall panel parts, improve the assembly precision analysis, and improve the accuracy and reliability of engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a simplified model diagram of the skin, ribs, skin tooling, and rib fixtures in the embodiment of the present invention;

[0039] Figure 2 Schematic diagram of the structure of a multi-matrix vacuum suction cup flexible tooling in an embodiment of the present invention;

[0040] Figure 3 A distribution diagram of positioning clamping points and key characteristic points on the skin in an embodiment of the present invention;

[0041] Figure 4 is a flow chart of an embodiment of the present invention.

[0042] In the figure, 1. rib a, 2. skin, 3. rib b, 4. rib fixture force sensor, 5. rib c, 6. rib fixture, 7. positioning point, 8. rib clamping point, 9. wall panel fixture clamping point, 10. interference connection point, 11. key feature point, 12. adjustable column, 13. support seat, 14. Y-axis screw, 15. rack, 16. X-axis transmission base, 17. base, 18. X-axis screw DETAILED DESCRIPTION

[0043] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0044] Example

[0045] This embodiment provides a method for analyzing the flexible assembly deviation of a laminated structural part under interference connection. The laminated structural part includes a wall panel part and a positioning part. In this embodiment, the laminated structural part is a composite thin-walled skin and three ribs on an aircraft wall panel assembly. The skin is the wall panel part, and the rib is the positioning part. The rib is clamped and positioned by a rib fixture. Figure 1 As shown, three ribs, namely rib a1, rib b3 and rib c5, are positioned on the inner surface of the skin 2, and the skin and the three ribs are assembled by a flexible tooling, namely a multi-matrix vacuum suction cup flexible tooling.

[0046] like Figure 2 As shown, the multi-matrix vacuum suction cup flexible tooling is mainly composed of an adjustable column 12, a support seat 13, a Y-axis lead screw 14, a rack 15, an X-axis transmission base 16, a base 17 and an X-axis lead screw 18. In the simplified model above, the adjustable columns 12 of the multi-matrix vacuum suction cup flexible tooling can be simplified to six cylindrical adjustable columns 12 on the main positioning surface. The adjustable columns 12 have the functions of integrating positioning and clamping, and the vacuum suction cup can generate a sufficiently large vacuum suction force to fix the skin 2 on the flexible tooling, making the positioning and clamping of the skin 2 more portable and efficient, and providing a more reliable guarantee for the subsequent assembly deviation analysis.

[0047] The rib clamp force sensor 4 is arranged at the clamping head of the rib clamp 6 to perform real-time measurement of the clamping force of the rib clamp 6 during the clamping process and to achieve more precise positioning of the skin 2. A groove pin combination is arranged on the side of the skin 2.

[0048] like Figure 3 The figure shows the distribution diagram of the positioning points 7, rib clamping points 8, wall panel tooling clamping points 9, interference connection points 10, and key feature points 11 on the skin 2 of this embodiment. A hole pin combination is set on the positioning point 7 on one side of the wall panel to position the skin 2 and the base 17. The rib clamping points 8 are arranged at both ends of the rib clamp 6 and the skin 2, and the rib is positioned and clamped on the wall panel 2 by the rib clamp 6. Eight interference connection points 10 are distributed on the mating surface of each rib and the wall panel, and the rib and the wall panel are connected together by interference connection. The key feature points 11 are evenly distributed on the skin 2, and the key feature points 11 are located between the ribs, which are used to detect the assembly errors of certain key points on the skin 2 to make the analysis more accurate. It should be noted that the number of positioning points 7, rib clamping points 8, wall panel tooling clamping points 9, interference connection points 10, and key feature points 11 on the skin 2 is not limited to the number listed in this embodiment, and the corresponding number can be increased or decreased according to actual conditions.

[0049] like Figure 4 As shown, this embodiment is specifically implemented according to the following contents:

[0050] Step 1: Obtain the initial stiffness matrix of skin 2: Perform finite element analysis on the ideal model of skin 2, and obtain the initial stiffness matrix of skin 2 [K n ].

[0051] Step 2, use flexible tooling to position and clamp the skin 2 according to the N-2-1 positioning principle: place the skin on the array vacuum suction cup flexible tooling, with the outer surface of the skin as the main positioning surface, and based on the N-2-1 positioning principle, arrange six positioning and clamping elements to position and clamp the skin, and at the same time, use the groove pin combination set on the side of the skin to achieve precise positioning of the skin; it is worth noting that other tooling or methods can also be used to position and clamp the skin 2 according to the N-2-1 positioning principle, and are not limited to multi-point array vacuum suction cup flexible tooling.

[0052] Step 3, positioning and clamping the rib according to the skin 2: using the inner surface of the skin 2 as the reference plane, positioning the rib in combination with the two assembly holes distributed at both ends of the rib, and temporarily fastening the rib to the skin 2 using process bolts.

[0053] Step 4: Measure the gap value at the characteristic point of the jth rib and the skin mating surface Measure the manufacturing error V of the key feature points of the skin and the jth rib mating surface in the normal direction respectively s j and V t j , V s j is the manufacturing error of skin 2 in the normal direction, V t j is the manufacturing error of the rib in the normal direction, 1≤j≤n, n is the total number of ribs, n=3, the clearance value between the skin and the rib at their mating surface is obtained by subtracting the normal manufacturing error value between the skin and the rib, and the clearance value between the jth rib and the skin 2 at the corresponding key feature point is obtained

[0054] Step 5: Collect the clamping force of the rib fixture 4: Clamp the jth rib with the rib fixture 4 to make the jth rib fit completely with the mating surface of the skin 2. The force sensor of the rib fixture 4 arranged on the jth rib measures and collects and records the three-axis force F at the measured point. n 、F τ 、F ξ .

[0055] Step 6: Calculate the stress field σ along the layer of skin 2 under interference connection j :The jth rib is connected to the skin 2 through interference connection. The internal stress of the composite plate under the interference connection of the hole is solved by the finite element analysis software abaqus to obtain the surface stress field distribution σ around the hole j .

[0056] Step 7: Update the stiffness matrix: Update the clamping force F of the fixture n 、F τ 、F ξ The stress field along the layer at the interference connection with skin 2 is j Load it onto the finite element model of skin 2 to obtain the global stiffness matrix [K j ].

[0057] Step 8: Unload the fixture on the rib, and the skin 2 is deformed. The springback of all key feature points on the skin 2 after the rib interference connection is obtained based on the influence coefficient method, including

[0058] Based on the linear elastic assumption, the gap value between the jth rib and skin 2 at the corresponding key feature point is As the input deviation, a linear relationship between the deviation source deviation and the assembly deviation is established, and the influence coefficient method is used to establish a linear relationship between the gap between the skin 2 and the rib at the interference connection point and the springback of the interference connection:

[0059]

[0060] In formula (20), is the springback of all key feature points on skin 2 after the j-th rib interference connection, [S] is the sensitivity matrix;

[0061] The initial stiffness matrix [K n ], calculate the unit displacement U generated at the clamping point of skin 2 under this loading stiffness i , the clamping force F required at the clamping point i , F i It is also equal to the unit resilience of each clamping point when the j-th rib clamp 6 is released;

[0062] [F i ]=[K n ]·U i (twenty one)

[0063] In formula (21), [F i ] indicates that the clamping point produces a unit displacement U j Unit clamping force matrix under ;

[0064] The unit rebound force F i Load it onto the assembly to calculate the deformation of skin 2, where the stiffness matrix of the assembly is the global stiffness matrix of skin 2 after obtaining the interference connection [K j ],

[0065]

[0066] According to formula (22), the unit rebound deformation U of the skin under the unit rebound force is calculated j ;

[0067] Calculate the rebound deformation of skin 2: Set the gap value Substitute into formula (20) to obtain the skin 2 unit rebound deformation U under unit rebound force j , where the influence coefficient matrix [S] is:

[0068] [S]=[K n ] -1 ·[K j ]·U j (twenty three).

[0069] Step 9: Substitute the springback values ​​of all key feature points on the skin 2 obtained in step 8 into the gap values ​​between the j+1th to nth ribs and the mating surface of the skin to obtain the springback deformation of the skin at the mating surface between the j+1th to nth ribs and the skin, where the springback deformation of the skin at the mating surface between the j+1th rib and the skin is:

[0070]

[0071] In formula (24), It represents the springback deformation of skin 2 at the mating surface between the j+1th rib and skin 2 after the jth rib is interfered with; It represents the springback deformation of skin 2 at the mating surface between the j+1th rib and skin 2 before connecting the jth rib.

[0072] Step 10. Repeat steps 4-9 until the last rib is clamped and record the displacement U of the last skin concern point. f , That is, the final assembly deviation V of the composite skin is obtained. f .

Claims

1. A method for analyzing the flexible assembly deviation of a laminated structural part under interference connection, wherein the laminated structural part comprises a wall panel part and a positioning part, the positioning part is clamped and positioned by a fixture, the wall panel part and the positioning part are assembled by a flexible tooling, the wall panel part and the positioning part are interference connected, and the method is characterized in that: The specific implementation is as follows: Get the initial stiffness matrix of the panel parts; Flexible tooling is used to position and clamp the wall panel parts according to the N-2-1 positioning principle; According to the position of the wall panel parts, the positioning parts are positioned and clamped, and the positioning parts are interference-connected with the wall panel parts one by one. After each interference connection of a positioning part, the springback amount of all key feature points on the wall panel parts after the interference connection of the positioning part is calculated based on the influence coefficient method, and the springback deformation amount of the wall panel parts at the mating surface of the next positioning part and the wall panel parts is calculated, until all the positioning parts are clamped, and the displacement of the key measurement feature points of the last wall panel parts is recorded, that is, the flexible assembly deviation of the laminated structure is obtained; The positioning parts are interference connected with the wall panel parts one by one, and after each interference connection with a positioning part, the springback amount of all key feature points on the wall panel part after the positioning part is interfered with and connected is calculated based on the influence coefficient method, and the springback deformation amount of the wall panel part at the mating surface of the next positioning part and the wall panel part is calculated until all the positioning parts are clamped. Specifically, it is as follows: Measure the gap value at the characteristic point of the mating surface between the positioning part and the wall panel part; clamp the positioning part by a fixture and measure the clamping force of the fixture; make interference connection between the wall panel part and the positioning part, and calculate the stress field along the layer at the interference connection of the wall panel part; load the clamping force of the fixture and the stress field along the layer at the interference connection of the wall panel part onto the finite element model of the wall panel part, and obtain the global stiffness matrix of the wall panel part after the interference connection; The fixture on the positioning part is unloaded, and the wall panel part is deformed. The springback amount of all key feature points on the wall panel part after the interference connection of the positioning part is obtained based on the influence coefficient method. According to the springback amount of all key feature points on the wall panel part obtained at this time, the springback deformation amount of the wall panel part in the next clamping of the positioning part and the wall panel part matching surface is calculated; The specific gap value of measuring the characteristic point of the matching surface between the positioning part and the wall panel part is: Measure the manufacturing errors of the key feature points of the panel parts and the positioning parts in the normal direction respectively and , the positioning part is the jth positioning part, is the manufacturing error of the panel parts in the normal direction, is the manufacturing error of the positioning part in the normal direction, , n To locate the total number of parts, n is a natural number that is not 0, the gap value between the jth positioning part and the wall panel part at the corresponding key feature point ; The method of clamping the positioning part by a fixture and measuring the clamping force of the fixture is specifically as follows: The jth positioning part is clamped by a fixture so that the jth positioning part and the matching surface of the wall panel part are completely fitted together. The force sensor set on the jth positioning part is used to measure, collect and record the three-axis forces of the measured point, which are F n 、F τ 、F ξ ; The wall panel parts are connected with the positioning parts by interference, and the stress field along the layer at the interference connection of the wall panel parts is calculated as follows: Connect the jth positioning part to the wall panel part through interference connection, solve the internal stress of the wall panel part at the interference connection through finite element analysis, and obtain the stress field distribution σ around the interference connection j ; After the interference connection of the positioning parts is calculated based on the influence coefficient method, the springback amount of all key feature points on the wall panel parts is specifically: Based on the linear elastic assumption, the gap value between the jth positioning part and the panel part at the corresponding key feature point is As the input deviation, a linear relationship between the deviation source deviation and the assembly deviation is established, and the influence coefficient method is used to establish a linear relationship between the gap between the wall panel parts and the positioning parts at the interference connection point and the springback of the interference connection: （20） In formula (20), is the springback amount of all key feature points on the panel parts after the jth positioning parts are connected by interference, [S] is the sensitivity matrix; The initial stiffness matrix of the panel part [K n ], calculate the unit displacement U generated at the clamping point of the wall panel parts under the loading stiffness i , the unit clamping force F required at the clamping point i , F i It is also equal to the unit rebound force of each clamping point when the rib j clamp is released; （21） In formula (21), [F i ] indicates that the clamping point produces a unit displacement U i Unit clamping force matrix under ; The unit rebound force F i Load it onto the assembly to calculate the deformation of the panel parts, where the stiffness matrix of the assembly is the global stiffness matrix of the panel parts after interference connection [K j ], （22） According to formula (22), the unit rebound deformation U of the wall panel parts under the unit rebound force is calculated j ; Calculate the springback deformation of the panel parts: Set the gap value Substitute into formula (20) to obtain the unit springback deformation of the wall panel part , where the influence coefficient matrix [S] is: （23）； The springback deformation of the wall panel part at the mating surface of the next positioning part and the wall panel part is: （24） In formula (24), It represents the springback deformation of the wall panel part at the mating surface between the j+1th positioning part and the wall panel part after the jth positioning part is interfered with. It represents the springback deformation of the wall panel part at the mating surface between the j+1th positioning part and the wall panel part before connecting the jth positioning part; Repeat the above operation each time a positioning part is clamped and fixed. In this way, until the last interference connection hole is connected, the springback amount of all key feature points is calculated.

2. The method for analyzing flexible assembly deviation of laminated structural parts considering interference connection according to claim 1, characterized in that: The method of obtaining the initial stiffness matrix of the wall panel part specifically includes performing finite element analysis on an ideal model of the wall panel part, and obtaining the initial stiffness matrix of the wall panel part by setting material property parameters of the wall panel part.

3. The method for analyzing flexible assembly deviation of laminated structural parts considering interference connection according to claim 1, characterized in that: The displacement of the last skinning concern point .

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